<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .wrap{

            margin: 0 auto;

            width: 80%;

        }

        #left{

            width: 200px;
            height: 500px;
            background-color: olivedrab;
            float: left;
        }

        #right{

            width: 200px;
            height: 500px;
            background-color: olivedrab;

            float: right;
        }

        #main{

            height: 500px;

            background-color: #B0B0B0;

            margin: 0 210px;
        }


    </style>
</head>
<body>

<div class="wrap">

    <aside id="left"></aside>
    <aside id="right"></aside>
    <section id="main"></section>
</div>

</body>
</html>